1. Field of the Invention
The present invention generally relates to an optical shutter device using an electrooptic material such as PLZT, or the like, for the optical modulation purpose used, for example, in an optical printer, and more particularly, to an optical shutter device wherein a plurality of chips of an electrooptic material each having a plurality of very small segments for the optical modulation purpose per a unit of dot are connected to each other.
2. Description of the Prior Art
In an optical shutter device of the type referred to above which uses an electrooptic material such as PLZT or the like, the quantity of the transmitting light passing through the PLZT chips is changed depending on the intensity of the driving voltage impressed on each of the plurality of very small segments of the chips as well as the length of the applying time. For example, when the optical shutter device is installed in an electrophotographic optical printer, the quantity of the transmitting light through the optical shutter device can be varied. Thus, it is possible to change the amount of light irradiated on the photoconductive photosensitive body. Accordingly, the electric charges on the photoconductive photosensitive body is decreased proportionally to the radiated light thereon, resulting in formation of a latent image which may be of a two tone image or a gray level image.
The conventional optical shutter device of the above-mentioned type has, however, the following problems.
The electrooptic material used in the optical shutter device is obtained through sintering at high temperatures and with high pressure, and therefore, the size of one chip of the electrooptic material is limited. If the optical shutter device is used in the optical printer, for example, it is necessary for the optical shutter device to have a length approximately equal to the length of one recording line, i.e., the recording width. Therefore, a plurality of the chips are aligned in a line to obtain the required optical shutter device. However, the half-wave voltage (or half-wavelength voltage) which is the voltage impressed across the electrooptical material to obtain the maximum transparency, differs for each chip because Of the variation of the electrooptic coefficient between the chips or the variation of gaps between independent electrodes and a common electrode. If the same driving voltage is impressed for recording, the recording results in non-uniform operation due to the difference of the characteristic of the electrooptic material, and the variation in the distance between the electrodes. As such, it is required to use chips of the electrooptic material having the characteristic as uniform as possible, which however lowers the yield of the chips for the optical shutter device, leading eventually to an increase of the cost of the optical shutter device itself.